The present invention relates to an impeller housing for a suction device. More particularly, it relates to an improved impeller housing which has reduced noise and improved airflow.
In a xe2x80x9cdirty airxe2x80x9d vacuum cleaner, the debris passes directly through the vacuum impeller chamber prior to being captured by the filter bag. In contrast, a xe2x80x9cclean airxe2x80x9d vacuum cleaner has the motor drawing the air and debris through the bag so that the bag captures the debris. The air only subsequently passes through the impeller chamber. The dirt path in a dirty air vacuum cleaner is very short compared to most clean air systems, which has advantages for cleaning performance. One disadvantage of dirty air motors is that they are typically louder than clean air motors. They also have a very loud tone noise. While not the largest contributor to the overall noise levels, the tone noise can be very annoying to consumers.
Tone noise typically occurs at a frequency that is seven times the rotation rate of the motor, which corresponds to the seven blades of the typical working fan. The motor cooling fan typically has twelve blades, is small, and may not, therefore, be a source of additional tone noise as was the case in the particular motor studied. The working fan blades cause the tone noise when they pass a geometric discontinuity in the volute shape. For example, FIG. 1 shows a cross section of the volute with the fan blades of an existing design. FIG. 1 also shows a geometric discontinuity at the motor outlet that causes tone noise. There is usually no geometric discontinuity at the motor inlet. Such discontinuities cause noise by interacting with the airflow leaving the ends of the blades. The airflow leaving the end of the blades is chopped by the discontinuities at the rate that the blades pass these discontinuities.
For noise control, there are two primary solutions. One is to isolate the noise source so that it is not heard; the other is to reduce the noise source. Isolating the noise source is an expensive choice. However, it does not require a good understanding of the noise source mechanism to be effective. The preferred solution is to reduce the source of noise.
Reducing the interaction of the airflow from the blade ends with the volute exhaust opening reduces the source of tone noise. Several ways to accomplish this are a) increasing the distance between the outer wall of the volute and the fan blade tips, b) reducing the fan rotation rate to reduce air velocity off the fan blade tips, and c) eliminating the geometric discontinuities, by moving the exhaust opening below the volute or on a different plane from the volute so that the fan blades are enclosed in a constant cross-section volute.
The first option, increasing the distance between the outer wall of the volute and the fan blade tips, has been used in several designs, but with limited success.
The second option, reducing the air velocity, reduces the noise level by approximately the velocity cubed. Reducing the air velocity would be accomplished by reducing the rpm of the motor or reducing the size of the working fan while maintaining the motor speed. Care must be taken when just reducing the size of the working fan because the motor would speed up due to the reduced load, which can result in the same velocities. If this solution were implemented, then the broadband noise would also be reduced because the broadband noise due to air turbulence decreases as the velocity decreases. However, reducing the fan rotation rate to reduce air velocity off the fan blade tips is not considered feasible because the current trend of U.S. vacuum cleaners has been to obtain as large an electrical amperage rating as possible.
Therefore, the third option, eliminating geometric discontinuities by moving the exhaust opening to below the volute or to a different plane from the volute, is the most feasible solution.
This option reduces the tone noise by removing the source of the noise. The goal is for the space around the fan tips to be in the shape of a uniform ring. Space is then provided for the air to exit behind the fan.
Accordingly, it has been considered desirable to develop a new and improved impeller housing which would overcome the foregoing difficulties and others and meet the above stated needs while providing better and more advantageous overall results.
The present invention relates to an impeller housing for a suction device. More particularly, it relates to an impeller assembly with an improved housing which has reduced noise and improved airflow.
The impeller assembly comprises a shaft and a housing. The housing comprises a plurality of walls. One of the walls comprises a volute. The plurality of walls can comprise a first wall, a second wall, a side wall connecting the first wall to the second wall, and a third wall extending from the first wall. The housing further includes a central axis, and an inlet port located along the central axis. The third wall forms an inlet passage extending from the inlet port. The shaft extends into the housing through the inlet port. The shaft is mounted along the central axis.
An outlet port is located on a second axis spaced from the central axis. An exhaust passage extends from the outlet port. The exhaust passage can increase in diameter along its length. The outlet port can be of a circular cross-section.
An impeller is mounted on the shaft for rotation. The impeller is located in the housing. The impeller includes a hub, and at least one blade extending from the hub. Each blade has a distal surface spaced from the shaft.
The impeller assembly further comprises a first plane which is approximately perpendicular to the central axis. The first plane contacts each blade distal surface. The impeller assembly also includes a second plane, parallel to and spaced apart from the first plane. The second plane contacts a wall of the outlet port at a location closest to the first plane.
The impeller blade can comprise a leading edge, a top edge and a trailing edge. The impeller can further comprise a backplate which supports the at least one blade. The backplate is positioned along the first plane.
A spacing wall is positioned between the volute and the wall of the outlet port to space each blade from the outlet port.
A top surface of the impeller can be generally parallel to a top surface of the impeller housing and the area between the top surface of the impeller and the top surface of the housing is minimized to reduce noise.
The impeller housing can include a first section and a second section to form a two-piece housing.
One advantage of the present invention is the provision of an air moving device having a new and improved impeller housing.
Another advantage of the present invention is the provision of an impeller housing with an exhaust passage which increases in diameter along its length.
Still another advantage of the present invention is the provision of an impeller housing accommodating an impeller. The blades of the impeller have a distal edge located on one side of a plane and an outlet port of the impeller housing is located on another side of the plane, thus reducing noise.
Yet another advantage of the present invention is the provision of an impeller housing in which the area between an upper surface of the impeller and an adjacent surface of the impeller housing is minimized to reduce noise.
Still yet another advantage of the present invention is the provision of an impeller housing with a spacing wall which is positioned between a volute of the housing and the outlet port of the housing to space the impeller blades from the outlet port thus reducing noise.
Still other benefits and advantages of the present invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed specification.